Microcalorimetric Method Research Articles

Magnetocaloric effect and heat capacity of high-spin manganese complexes in a disperse state

Magnetothermal properties of high-spin chloro(2,3,7,8,12,13,17,18-octaethylporphyrinato)manganese(III), chloro(5,10,15,20-tetraphenylporphyrinato) manganese(III), bromo(5,10,15,20-tetraphenylporphyrinato)manganese(III), and (acetato)(5,10,15,20-tetraphenylporphyrinato)manganese(III) complexes as 6% water suspensions were determined by the microcalorimetric method at 298 K in a magnetic field of 0–1.0 T. It was established that when the magnetic field was applied, the temperature of the systems increases, leading to positive values of the magnetocaloric effect: the higher the magnetic field induction, the higher the values. It is shown that the dependences of the heat capacity of the complexes’ solid particles on the magnetic field induction are of an extreme nature with a heat capacity in the area above 0.6 T less than that in the zero field. The regularities of the dynamics of the numerical values of the change in enthalpy and magnetic entropy of the manganese complexes when a growing magnetic field was applied and the regularities of the influence of the acidoligand in pentacoordinated complexes on their magnetothermal properties were considered.

Toxicity of three phenolic compounds and their mixtures on the gram-positive bacteria Bacillus subtilis in the aquatic environment

Although phenolic compounds are intensively studied for their toxic effects on the environment, the toxicity of catechol, resorcinol and hydroquinone mixtures are still not well understood because most previous bioassays are conducted solely using single compound based on acute tests. In this work, the adverse effect of individual phenolic compounds (catechol, resorcinol and hydroquinone) and the interactive effect of the binary and tertiary mixtures on Bacillus subtilis ( B. subtilis) using microcalorimetric method were examined. The toxicity of individual phenolic compounds follows the order catechol > resorcinol > hydroquinone with their respective half inhibitory concentration as 437, 728 and 934 µg mL − 1. The power–time curve of B. subtilis growth obtained by microcalorimetry is in complete agreement with the change in turbidity of B. subtilis against time, demonstrating that microcalorimetric method agrees well with the routine microbiological method. The toxicity data obtained from phenolic compound mixtures show that catechol and hydroquinone mixture possess synergistic effect while the other mixtures display additive joint actions. Furthermore, the concentration addition (CA) and independent action (IA) models were employed to predict the toxicities of the phenolic compounds. The experimental results of microcalorimetry show no significant difference on the toxicity of the phenolic compound mixtures from that predicted by CA. However, IA prediction underestimated the mixture effects in all the experiments.

Microcalorimetric Study on the Critical Micelle Concentration and Thermodynamic Functions of Di(2-ethyl-hexyl) Phosphate Salts in Organic Solvent +sec-Octyl Alcohol Systems at 298.15 K

The power−time curves of the micelle formation process were determined for three kinds of quasi-surfactants [lithium di(2-ethyl-hexyl) phosphate, sodium di(2-ethyl-hexyl) phosphate, and potassium di(2-ethyl-hexyl) phosphate] and five kinds of alkanes (octane, decane, dodecane, tetradecane, and hexadecane) with sec-octyl alcohol by titration microcalorimetry. The critical micelle concentration (CMC), aggregation number (n), formation constant of micelle (K), and thermodynamic functions (ΔrHmθ, ΔrGmθ, and ΔrSmθ) were obtained. For different quasi-surfactants and homologue of the alkanes, the relationships between the carbon number (N) of the alkanes with the critical micelle concentration (CMC) and the thermodynamic properties of the quasi-surfactants are discussed. It can be concluded as follows: (1) The microcalorimetric method is a good method to study the process of micelle formation. (2) The CMC decreased with an increase of the carbon number (N) of the alkanes, and the relative order of the CMC of different quasi-surfactants was D2EHPA(K) > D2EHPA(Na) > D2EHPA(Li) at the same carbon number. (3) The aggregation numbers (n) and formation constant of micelle (K) increased with an increase of the carbon number (N) of the alkanes. The relative order of different quasi-surfactants was D2EHPA(K) > D2EHPA(Na) > D2EHPA(Li) at the same carbon number. (4) The ΔrHmθ and ΔrSmθ increased, while ΔrGmθ decreased with an increase of the carbon number (N) of the alkanes. The relative order of the different quasi-surfactants was D2EHPA(Li) > D2EHPA(Na) > D2EHPA(K) at the same carbon number.

A microcalorimetric enzymatic method for trehalose determination in food

As trehalose is a glucose font and also an additive in food, a new reliable method for trehalose determination is proposed. The analytical method uses an isothermal microcalorimeter, directly relates the analyte concentration with the heat variation of the enzymatic decomposition of trehalose into two glucose molecules. The enzymatic reaction is performed inside the calorimeter in the presence of trehalase enzyme immobilized on amino activated glass beads. Through the calibration curve, the trehalose quantity in some food samples (mushrooms and honey) has been determined. The calorimetric procedure was compared to a previously identified methodology based on an amperometric biosensor.

Inhibitory study of two cephalosporins on E. coli by microcalorimetry

The microcalorimetric method has been used to study the effects of cefpiramide and ceftizoxime sodium on the E. coli growth. The results revealed that these two cephalosporins may alter the metabolic way of the E. coli. Moreover, the lethal doses of cefpiramide and ceftizoxime sodium are 2.000 and 0.2000 μg mL−1, respectively. Combining with the relationships between growth rate constant (k), the maximum power output (P m ), the time corresponding to the maximum power output (t m ) and cephalosporins concentration (C), one can draw the conclusion that the ceftizoxime sodium has a stronger inhibition effects on the growth of E. coli than that of cefpiramide and they both have the possibility to induce the drug fever.

Toxicity Effect of Pb(II) on Two Different Kinds of Microbes Measured by Microcalorimetry

AbstractIn this work, microcalorimetric technique was used to analyze Pb(II) toxic action on the metabolic activities of Candida humicola and Bacillus subtilis. The experimental results revealed that Pb(II) had a stimulating effect on C. humicola and B. subtilis growth at a relatively low concentration (10.0 g·mL−1); while, C. humicola and B. subtilis were inhibited completely when the concentrations were up to 320.0 and 160.0 g·mL−1, respectively, and the relationships between growth rate constant (k) and doses of Pb(II) were approximately linear for the two microbes at certain concerntrations. At the same time, their cell dry weight and turbidity (OD600) during growth were also obtained. Their thermogenic curves of the growth coincided well with their turbidity curves, elucidating that the microcalorimetric method agreed with the routine microbiology methods. All of these corroborate the validity and sensitivity of the microcalorimetric technique to investigate the toxic effect of Pb(II) on soil microorganisms.

Acute toxic effects of three pesticides on Pseudomonas putida monitored by microcalorimeter

A series of calorimetric experiments were performed to investigate the toxic effects of beta-cypermethrin (BCP), bensulfuron-methyl (BSM) and prometryne (PM) on Pseudomonas putida (P. putida). The metabolic action of P. putida on the three pesticides was studied by obtaining power-time curves. The growth of P. putida was inhibited completely in each case when the concentrations of pesticides were up to 80 μ g mL− 1. The relationships between the inhibitory ratio (k) and doses of contaminants were approximately linear for the three pesticides. The total heat dissipated per milliliter (Q total) for the pesticides decreased during the course of the experiment. The OD600 of P. putida growth in the absence and presence of pesticides was also obtained. The power-time curves of P. putida growth coincided with its turbidity curves. This elucidates that microcalorimetric method agrees well with the routine microbiological method. Among these three pesticides, BSM was found to be the most toxic with an IC 50 of 19.24 μ g mL− 1 against P. putida. PM exhibited moderate virulence with an IC 50 of 27.86 μ g mL− 1 and BCP had the lowest toxicity with an IC 50 of 39.64 μ g mL− 1.

The toxic effect of cadmium on pure microbes using a microcalorimetric method and a biosensor technique

A microcalorimetric technique based on microbes heat-output was explored to evaluate the effect of Cd (II) on Bacillus subtilis and Candida humicola. The power-time curves of the growth metabolism of Bacillus subtilis and Candida humicola and the effect of Cd (II) on it were studied by using a TAM III microcalorimeter, ampoules method at 28°C. For the evaluation of toxic effect on pure micro-organisms, the maximum peak-heat output power (P max) in the growth phase, the growth rate constants (k), the log phase heat effects (Q log), and the total heat effect (Q T) for Bacillus subtilis and Candida humicola were determined. Dissolved oxygen and biochemical oxygen demand (BOD) were evaluated by a biosensor. Cadmium has been regarded as the essential biological trace element. Cd (II) solutions of different concentration have different effects on Bacillus subtilis and Candida humicola growth metabolism. The higher concentrations of Cd (II) inhibit the growth of Candida humicola (1600–3200 μ g·mL−1), Bacillus subtilis (240–480 μg·mL−1); the lower concentrations can promote the growth of both micro-organism. The values of cell dry weight is also showed in conformity in the cell dry weight changes to the micro-organisms' growth time. Comparison of growth curves of two micro-organisms showed that both the trends of biochemical oxygen demand were exhibiting regressive changes with the passage of time during their generation times (t G). Results from ultraviolet spectrophotometer and precision pH meter all showed that the control growth curves were visioning same trends with the thermodynamic curves of micro-organisms measured by microcalorimeter.

Microcalorimetric Study on the Inhibition of Escherichia coli by Some Novel Pyridine Amide Schiff Base Derivatives

AbstractThe antibacterial effect of a series of novel pyridine amide Schiff base compounds on Escherichia coli was investigated by a microcalorimetric method at 37 °C. The metabolic power‐time curves of the bacteria treated by the compounds were obtained, and the thermokinetic parameters were analyzed, from which the antibacterial activities of these compounds were evaluated. The results show that two compounds F and G have good activity on aerobic multiplying metabolism of E. coli, with the value of IC50 106 and 113 mg/L respectively, but have no effective action on the fermentation metabolism of E. coli. The action of the compounds on the non‐multiplying metabolism was investigated by taking the heat output of E. coli in the stationary phase as the guideline of the activity. The experimental results revealed that the hydrophilicity of these Schiff bases had a great influence on their antibacterial activity, which results from the bacterial cell wall structure. The antibacterial structure‐activity relationship of these Schiff base derivatives was also briefly discussed. The antibacterial activity of the compounds against E. coli was as follows: compound F>G>C>D>E>B>A.

Microcalorimetric Studies of the Biological Effects of Ho(III) on Halobacterium halobium R1

The biological effect of Ho3+ on Halobacterium halobium R1 growth was analyzed using the microcalorimetric method. Using the LKB-2277 Bioactivity Monitor with the ampoule method at 37 degrees C, the thermogenic curves of the growth of H. halobium R1 were obtained. Then, the maximum power (P (m)) and the growth rate constants (k) were determined, and the values of P (m) and k were linked to the concentration of Ho3+. In all, the addition of Ho3+ cause a decrease in the maximum heat production and growth rate constants. To confirm the results, the shapes of H. halobium R1 cell addition with Ho3+ using a transmission electron microscope (TEM) were observed. According to the thermogenic curves and TEM photos of H. halobium R1 under different conditions, it is clear that the metabolic mechanism of H. halobium R1 growth has been changed with the addition of Ho3+.

Regularities of Magnetocaloric Effect and Determination of Some Thermodynamic Parameters for (Octaethylporphynato)chloro-manganese(III)

Magnetocaloric effect (MCE) and specific heat capacity of (2,3,7,8,12,13,17,18-octaethylporphynato)chloromanganese(III) (6% suspension in water) were measured by microcalorimetric method in the dependence of temperature (298-353 K) and magnetic field (0-0.7 T). It is found that the MCE has positive value which increases with growth of the magnetic field induction at all the temperatures and decreases with the temperature growth at all the magnetic fields. Breaking the magnetic field leads to adiabatic demagnetizing. The dependence of specific heat capacity of the studied system from the value of magnetic field induction has maximum at 0.2-0.3 T at all the temperatures. When the induction value is higher than 0.6 T the specific heat capacity value is less than that in zero field. The temperature growth leads to the increase of the specific heat capacity in all the magnetic fields. On the base of the experimental data on the magnetocaloric effect and specific heat capacity of the manganese complex the dependencies of enthalpy, of the magnetic components of molar heat capacity and entropy from the temperature and magnetic induction are calculated.

Studies on CMC and thermodynamic function of anionic surfactants in DMA/long-chain alcohol systems using microcalorimetric method

The critical micelle concentration (CMC) and the thermodynamic function of the anionic surfactant, sodium laurate (SLA) and sodium dodecyl sulfate (SDS) in the N,N-dimethyl acetamide (DMA)/long-chain alcohol systems were studied using titration microcalorimetric method. The power-time curves of SLA and SDS in the presence of a long-chain alcohol (n-heptanol, n-octanol, n-nonanol, n-decanol) in the DMA medium were determined. Then, from the curves, the critical micelle concentration (CMC) and the thermodynamic standard formation functions (ΔH ϑ m, ΔG ϑ m and ΔS ϑ m) were obtained through thermodynamic theories. The relationships between temperature, alcohol’s carbon number, concentration and thermodynamic properties were discussed. For SLA or SDS in a DMA solution, under the same concentration of alcohol, the values of CMC, ΔH ϑ m and ΔS ϑ m increase, while the value of ΔG ϑ m decrease with the increase of temperature. Under the same condition of identical temperature and alcohol concentration, the values of CMC, ΔH ϑ m, ΔG ϑ m and ΔS ϑ m decrease with the increase of the alcohol’s carbon number. In the presence of the same kind of alcohol, the values of CMC and ΔG ϑ m increase, but the values of ΔH ϑ m and ΔS ϑ m decrease with the concentration increases in alcohol series at the same temperature.

Microcalorimetric investigation of the toxic action of ammonium ferric(III) sulfate on the metabolic activity of pure microbes

A series of calorimetric experiments were performed to investigate toxic action of ammonium ferric sulfate (AFS) on Bacillus subtilis, Pseudomonas putida and Candida humicola. The power–time curves of micro-organism metabolism were obtained, and the action of them by addition of AFS was studied. C. humicola, B. subtilis and P. putida were inhibited completely when the concentrations were up to 320.0, 160.0 and 160.0 μg mL −1, respectively. The relationships between growth rate constant ( k) and doses of AFS were approximately linear for three microbes, P. putida for 10.0–160.0 μg mL −1 ( R = −0.9746), B. subtilis for 0–160.0 μg mL −1 ( R = −0.9868) and C. humicola for 10.0–320.0 μg mL −1 ( R = −0.9955). The total heat dissipated per milliliter ( Q T) for three microbes remained balance approximately during the lower doses, P. putida and B. subtilis less than the dose of 20.0 μg mL −1, 0.56 ± 0.01 and 0.26 ± 0.01 J mL −1, respectively, C. humicola less than the dose of 40.0 μg mL −1, 0.58 ± 0.03 J mL −1. The biomass and OD 600 of three micro-organisms growth in the absence of AFS also were obtained. The power–time curve of C. humicola growth coincided with its turbidity curve. It elucidates that microcalorimetric method agreed with the routine microbiology method.

Calorimetric analysis of three hydroxy acids as markers for quality and safety in food

A new analytical methodology to quantify three hydroxy acids (orotic, ascorbic, L-malic acids), by isothermal solution microcalorimetry, was outlined and applied to different foods. Three specific enzymatic reactions were used to ensure the correctness of the results. The considered acids can be considered as markers in food quality for their biochemical peculiarities. The enzymatic microcalorimetric method is very reliable and linearity is satisfied in the concentration ranges useful for food analyses. The analytical results of the underlined method are very accurate, precise, sensitive and in good agreement with the values obtained with other common methods.

Microcalorimetric Studies on Gene Promoter Function of Cloned DNA Fragements from Halobacterium halobium J7 Plasmid pHH205 in Escherichia coli TG1

AbstractHalobacterium halobium is a typical kind of extremely halophilic bacterium. Combined with the antibiotic resistance assay, the microcalorimetric method was used to study the promoter function of the cloned DNA fragments from Halobacterium halobium J7 plasmid pHH205 in Escherichia coli TG1. The promoter probe vector, plasmid pKK232‐8, was used to form the recombinants. The DNA fragment, which is the promoter for the chloramphenicol acetyl transferase (CAT) gene in plasmid pKK232‐8, is about 800 bp, and the chloramphenicol resistance level presented by IC50 is about 200 µg·mL−1, which suggests a high promoter activity. The conclusions show that there probably exist double‐function or trinary‐function gene promoters in Halobacterium halobium, and Archaea may contain rich genetic resources.

An in vitro microcalorimetric method for studying the toxic effect of cadmium on microbial activity of an agricultural soil

Using TAM III multi-channel thermocalorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant (k), peak-heat output power (P (max)) and the number of living microorganisms decreased with increasing concentration of Cd. Anncrease in Cd concentration resulted in the decrease of the peak-heat output power and increase in the time of the peak of power. However, the relationships between the thermokinetic parameters (k and P (max)) and the number of microorganism were not linear, but the trend was similar. Our research also suggests that microcalorimetry is a very sensitive, simple and useful technique for in vitro investigation of the effects of toxic heavy metals on soil microbial activity.

Effect of Alcohols on the CMC and Thermodynamic Functions of Anionic Surfactants in DMF/Long‐Chain Alcohol Using Microcalorimetric Method

The critical micelle concentration (CMC) of two kinds of anionic surfactant (including sodium laurate (SLA) and sodium dodecyl sulfate (SDS)) in mixed alcohol and N, N‐dimethyl formamide solvent (DMF) were investigated through measuring power‐time curves by titration microcalorimetry. From data of the lowest point and the area of the power‐time curves, their CMC and ΔH m 0 can be obtained. According to standard thermodynamic equations, ΔG m 0 and ΔS m 0 also can be calculated. For different surfactant, the influences of the carbon number and the concentration of alcohol on the CMC and standard thermodynamic functions are different in DMF polar medium. These thermodynamic functions for micelle formation can be further interpreted.

Antibacterial Activity of a Kind of Novel Schiff Base and Its 3 d,4 f Complexes

The microcalorimetric method was used to study the antibacterial activity on the bacteria's multiplying metabolism and the non-multiplying metabolism. The metabolism thermogenic curves of Escherichia coli ( E. coli) and Staphylococcus aureus ( S. aureus), under the action of the synthesized Schiff base and its 3 d,4 f complexes (2L, 2LZnYb), were obtained. The results showed that the multiplying metabolism and the non-multiplying metabolism of bacteria could be analyzed by the thermogenic curves using the thermokinetic equations. On the multiplying metabolism, the two compounds (2L, 2LZnYb) have strong activity for E. coli. (IC 50 (half-inhibitory concentration) is 6.1 and 5.1 mg·L −1, respectively) and weak activity for S. aureus (IC 50 is 310.1 and 595.9 mg·L −1, respectively). The introduction of Zn and Yb with the compound slightly increased the inhibition on the multiplying metabolism of E. coli but greatly decreased the effect on that of S. aureus. The activity of these two compounds showed great difference on the non-multiplying metabolism. Regardless of E. coli or S. aureus, 2L showed a notable inhibition and MSC 50 (the minimum stationary-cidal concentration 50) of 2L was 6.4 and 209.7 mg·L −1 for the two microorganisms, respectively. Thus, 2L may become a novel kind of potential antibacterial candidate.

Photopolymerization reactions initiated by a visible light photoinitiating system: Cyanine dye/borate salt/1,3,5‐triazine

AbstractNew three‐component photoinitiating systems consisting of a cyanine dye, borate salt, and a 1,3,5‐triazine derivative were investigated by measuring their photoinitiation activities and through fluorescence quenching experiments. Polymerization kinetic studies based on the microcalorimetric method revealed a significant increase in polymerization rate when the concentration of n‐butyltriphenylborate salt or the 1,3,5‐triazine derivative were increased. The photo‐induced electron transfer process between electron donor and electron acceptor was studied by means of fluorescence quenching and SrEt change of the fluorescence intensity. The experiments performed documented that an increase of the n‐butyltriphenylborate salt concentration dramatically increases the rate of dye fluorescence quenching, whereas the increasing of the 1,3,5‐triazine derivative concentration slows down the consumption of the dye. We conclude that the primary photochemical reaction involves an electron transfer from the n‐butyltriphenylborate anion to the excited singlet state of the dye, followed by the reaction of the 1,3,5‐triazine derivative with the resulting dye radical to regenerate the original dye. This reaction simultaneously produces a triazinyl radical anion derived from the 1,3,5‐triazine, which undergoes the carbon‐halogen bond cleavage yielding radicals active in initiation of a free radical polymerization chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3626–3636, 2007

Microcalorimetry studies of phase transitions in (BaxSr1−x)TiO3

Both temperatures, T C, (T C —Curie temperature) and heat of the phase transition: ferroelectric-paraelectric, ΔH, in the BaxSr1−xTiO3 materials have been studied by means of the microcalorimetric method. The determined parameters were verified by either temperature dependence of the dielectric permittivity (Curie-Weiss law) or thermodynamic method. The effect of strontium content on T C has been discussed. It was found that microcalorimetry is useful tool studying phase transition phenomena in ferroelectric perovskites.